java+spark: org.apache.spark.SparkException: Job aborted: Task not serializable: java.io.NotSerializableException

Question

I'm new to spark, and was trying to run the example JavaSparkPi.java, it runs well, but because i have to use this in another java s I copy all things from main to a method in the class and try to call the method in main, it saids

org.apache.spark.SparkException: Job aborted: Task not serializable: java.io.NotSerializableException

the code looks like this:

public class JavaSparkPi {

public void cal(){
    JavaSparkContext jsc = new JavaSparkContext("local", "JavaLogQuery");
    int slices = 2;
    int n = 100000 * slices;

    List<Integer> l = new ArrayList<Integer>(n);
    for (int i = 0; i < n; i++) {
        l.add(i);
    }

    JavaRDD<Integer> dataSet = jsc.parallelize(l, slices);

    System.out.println("count is: "+ dataSet.count());
    dataSet.foreach(new VoidFunction<Integer>(){
        public void call(Integer i){
            System.out.println(i);
        }
    });

    int count = dataSet.map(new Function<Integer, Integer>() {
        @Override
        public Integer call(Integer integer) throws Exception {
            double x = Math.random() * 2 - 1;
            double y = Math.random() * 2 - 1;
            return (x * x + y * y < 1) ? 1 : 0;
        }
    }).reduce(new Function2<Integer, Integer, Integer>() {
        @Override
        public Integer call(Integer integer, Integer integer2) throws Exception {
            return integer + integer2;
        }
    });

    System.out.println("Pi is roughly " + 4.0 * count / n);
}

public static void main(String[] args) throws Exception {

    JavaSparkPi myClass = new JavaSparkPi();
    myClass.cal();
}
}

anyone have idea on this? thanks!

Answer 1

The nested functions hold a reference to the containing object (JavaSparkPi). So this object will get serialized. For this to work, it needs to be serializable. Simple to do:

public class JavaSparkPi implements Serializable {
  ...